>My perception is that HN got pickier,

While HN is part of the set, I think we need to look larger. Is it just HN, or is it everywhere? If it's not everywhere, what percentage of sites is it? What are the sites that don't have this issue like or do different.

I think part of it is that HN has grown a lot because of a lot of other sites getting worse. The problem is that growing makes it worse. Then add on top of that there are a lot of high value targets here on HN that bots try to target, financially or politically.

Internet is a messy place now. I remember years and years ago, like early 2000s people thought that things like astro-turfing weren't real, and governments were not targeting individuals/groups on forums. How nieve their were.